NEUROLEPTICS

NEUROLEPTICS


NEUROLEPTICS

  • Also known as “Antipsychotics”.
  • Mainstay of treatment for schizophrenia, schizoaffective disorders & delusional disorders.

Classification:

  • Typical antipsychotics/1st generation antipsychotics/dopamine receptor antagonists (DRAs).
  • Atypical antipsychotics/2nd generation antipsychotics/serotonin-dopamine antagonists.

TYPICAL ANTIPSYCHOTICS:

  • MOA: Mainly act through dopamine, D2 receptor antagonism in mesolimbic tract.

Actions:

  • Effective against positive symptoms.
  • Minimal effect on negative symptoms.

Sub-classifications:

According to chemical groups – 

  • Phenothiazines: Chlorpromazine, Thioridazine, Trifluoperazine, Prochlorperazine, Triflupromazine, Fluphenazine, Perphenazine.
  • Thioxanthenes: Thiothixene, flupenthixol.
  • BuUrophenonesi Haloperidol, droperidol, penfluridol.
  • Miscellaneous: Pimozide, loxapine, molindone.

According to potency – 

  • Low potency – Chlorpromazine & thioridazine.
  • High potency – Haloperidol & fluphenazine.

Side effects:

  • Movement disorders – Extrapyramidal symptoms (acute dystonia, acute akathisia, drug-induced parkinsonism, tardive dyskinesia, neuroleptic malignant syndrome, hyperprolactinemia, sedation, orthostatic hypotension & anticholinergic side effects.

ATYPICAL ANTIPSYCHOTICS:

MOA:

  • Act through antagonism of 5Ht-2 receptors & D2 receptors.
  • Higher ratio of 5 HT2 to D2 blockade.

Actions: 

  • Effective in treatment of both positive & negative symptoms.
  • Lesser risk of causing extrapyramidal side effects as well as hyperprolactinemia – Due to lesser D2 blockade.

Drugs included –

  • Clozapine, Olanzapine, Risperidone, Paliperidon, Iloperidone, Quetiapine, Ziprasidone, Aripiprazol, Sertindole, Zotepine, Lurasidone, Asenapine & Amisulpride

Side effects – 

  • Movement disorder – Lesser incidence.
  • Hyperprolactinemia – Lesser incidence.
  • Weight gain.
  • Increased risk of dyslipidemia, diabetes & cardiovascular disease.
  • Sedation, QTc prolongation (especially with ziprasidone).
  • Seizures.

Important points on antipsychotics:

  • Long-acting injectable antipsychotics (Depot anti-psychotics):
    • Used in poorly compliant patients.
    • IM injection once a month/fortnight.

Durgs: 

  • Flupenthixol, Fluphenazine, Haloperidol, Pipotiazine, Zuclopenthixol, Risperidone, Olanzapine, Paliperidone & Aripiprazole.

Thioridazine:

  • Cause irreversible retinal pigmentatlon.
  • Cause cardiac arrhythmias (prolongation of QT interval)
  • Drug with least extrapyramidal side effects (Among typical antipsychotics).

Chlorpromazine:

  • Cause corneal & lenticular deposits.

Penfluridol:

  • Longest acting antipsychotic.

Ziprasidone:

  • Cause cardiac arrhythmias (prolongation of QT interval)

Aripiprazole:

  • Partial agonist at D2 receptors
  • (all other antipsychotics are D2 antagonists).

Exam Important

  • Neuroleptics are also known as “Antipsychotics”.
  • Antipsychotics are mainstay of treatment for schizophrenia, schizoaffective disorders & delusional disorders.
  • Typical antipsychotics mainly acts through dopamine, D2 receptor antagonism in mesolimbic tract.
  • Extrapyramidal symptoms (acute dystonia, acute akathisia, drug-induced parkinsonism, tardive dyskinesia, neuroleptic malignant syndrome, hyperprolactinemia, sedation, orthostatic hypotension & anticholinergic side effects are all most important side effects associated with typical antipsychotics.
  • Atypical antipsychotics act via antagonism of 5Ht-2 receptors & D2 receptors.
  • Lesser risk of extrapyramidal side effects & hyperprolactinemia is observed with atypical antipsychotics due to lesser D2 blockade.
  • Lesser incidence of movement disorder & hyperprolactinemia is seen with atypical antipsychotics.
  • Long-acting injectable antipsychotics (Depot anti-psychotics) are used in poorly compliant patients.
  • Thioridazine causes irreversible retinal pigmentation & cardiac arrhythmias.
  • Chlorpromazine causes corneal & lenticular deposits.
  • Penfluridol is longest acting antipsychotic.
  • Ziprasidone cause cardiac arrhythmias
  • Aripiprazole is a partial agonist at D2 receptors (all other antipsychotics are D2 antagonists).
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